I was actually going to make a thread about this a few days ago, but my browser crashed and I was too lazy to rewrite it.
The HOI2 editor works with AOD. It also wasn't completely finished, but you can find the thread and download links
here.
I've found it most useful for arranging tech trees. It took longer to create the background image for this tech tree than it took to reorganize the default AOD techs (once a more efficient tree design was determined).
Although it basically takes the information and then outputs it into a 'new' text file, so if you are writing things manually and putting comments in you will lose them. It also doesn't recognize some of AOD's added commands (like night attack modifiers), but if you put those in manually it will keep what you had if you do run the editor.
As far as I know leaders haven't changed, so you shouldn't encounter any problems. But it's not a validator, so I'm not sure if it will be able to parse your edited leader files if the game can't.
In that case you may want to start from scratch (and I'd recommend using something like Notepad++ to help keep semi-colons better organized). I believe there's also a Clausewitz/Europa engine validator. But that too is somewhat out of date and didn't work well with steam and AOD's mod-dir set-up when I tried it.